Opioid drugs increase glial cell activation and consequent cytokine release. These changes in glial cell activation may be related to the abuse liability of opioid drugs including heroin and prescription opioids. Data supporting this hypothesis have demonstrated that glial cell attenuators decrease the positive rewarding aspect of opioids in laboratory animals. Ibudilast (MN-166, formerly AV411) is a compound that inhibits the activation of glia and thereby inhibits the release of cytokines. Recent preclinical studies demonstrate that while ibudilast increases the analgesic effects of opioids, it decreases the rewarding effects of such drugs. It has also been shown that ibudilast suppresses morphine-induced release of dopamine, a primary neurotransmitter involved in the rewarding and reinforcing effects of abused drugs. Additionally, we recently found that ibudilast decreases subjective symptoms of opioid withdrawal in opioid dependent humans during detoxification.